Background: The concept of evaluating bioequivalence has changed over a period of time. Currently, the Average Bioequivalence approach (ABE) is the gold standard tool for the evaluation of generics. Of late, many debates had arisen about employing ABE approach for the appraisal of all drug categories. This review aims to examine the limitations of ABE approach and the significances of Population Bioequivalence (PBE) and Individual Bioequivalence (IBE) approach, current regulatory thinking for assessing different categories of the drug, whether they are adequately assessed, and the evaluation is in the right direction. Methods: We carried out an organized search of bibliographic databases for peer-reviewed research literatures, regulatory recommendations, guidance documents using a focused review question and eligibility criteria. The standard tools were used to appraise the quality of retrieved documents and to make sure the authenticity of the data. Results: In total 73 references were used in the review, the majority of the references (guidance documents) were from the different regulatory agencies and product-specific guidance. There were 29 product-specific guidance from USFDA and EMA. The limitations of the ABE approach were discussed in detail along with the significances of Population Bioequivalence (PBE) approach and Individual Bioequivalence (IBE) approaches. Conclusion: It is apparent from the review that IBE approach is a precise method for evaluating the drugs as it answers drug interchangeability (prescribability and switchability). IBE approach is followed by PBE approach and ABE approach for the evaluation of different categories of drugs in terms of precision.

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Background: Bioequivalence studies are a vital part of drug development. The average bioequivalence approach is the standard method of assessment to conclude whether the generic product is bioequivalent to the innovator product. Of late, debates are on whether the average bioequivalence approach adequately addresses drug interchangeability as it considers only population mean for the evaluation especially when highly variable drug products and narrow therapeutic index drugs are dealt with. Hence, the alternative approaches like population bioequivalence and individual bioequivalence assessment approaches emerge as they consider inter/intra-subject variance and subject- by-formulation variance along with population mean. Objectives: The objective of the study was to apply different bioequivalence assessment approaches in a replicate bioequivalence study to evaluate the drug interchangeability. Methods: This was an open-label, single-dose, randomized, balanced, two-treatment, three-period, three-sequence, partial replicate crossover bioequivalence study of omeprazole enteric-coated tablet 20 mg conducted on 48 normal healthy subjects under fed conditions. The plasma concentration of omeprazole was analyzed by a validated bioanalytical method to determine the pharmacokinetic and statistical parameters to assess average bioequivalence, population bioequivalence, and individual bioequivalence. Results: In this study, test formulation was shown to be bio-inequivalent to the reference formulation by average bioequivalence, population bioequivalence, and individual bioequivalence approaches. Conclusion: The outcome of the evaluation clearly states that the bioequivalence outcome of all these approaches are the same. Obviously, it does not mean that these three approaches provide the same outcome though the consideration of variances varies. Certainly, population bioequivalence and individual bioequivalence approach will be more accurate for the assessment of drug interchangeability.

The assessment of interchangeability (prescribability and switchability) is one of the debatable topics in the generic drug industry. Currently, the question is whether we have an adequate assessment system for the evaluation of generic drug products. The objective of the study is to assess the comparative oral bioavailability of Itraconazole capsule 100mg after administering single dose to adult, healthy, human subjects in fasted state by different bioequivalence approaches like  average bioequivalence (ABE), population bioequivalence (PBE) and individual bioequivalence (IBE) and to monitor the safety of study subjects. An open-label, balanced, randomized, two-treatment, two-sequence, four-period, crossover, single-dose comparative oral bioavailability study was conducted in sixteen healthy, adult, human subjects in a fasted state. Test formulation, Itraconazole capsule 100mg, and reference formulation, SPORANOX®  (Itraconazole) capsule 100mg, were administered in a fasted state. The test formulation, Itraconazole capsule 100mg, showed bio-inequivalent against reference SPORANOX®  (Itraconazole) capsule 100mg in study subjects under a fasted state. Also, the test formulation exhibited a similar safety and tolerability profile compared to the reference formulation. There was no report of serious adverse events (SAEs) and deaths in the study. The test formulation was found to be bio-inequivalent to reference formulation in the study subjects under a fasted state by estimating different bioequivalence approaches like average bioequivalence, population bioequivalence, and individual bioequivalence.

Background: In the drug development process, an assessment of bioequivalence is an integral part. For the evaluation of generics against the comparator, average bioequivalence approach is the gold standard method. In the recent past, there were many discussions on whether we have the adequate tool to evaluate generics and thereby drug interchangeability (prescribability and switchability) issue is addressed as average bioequivalence approach just considers population mean. Hence, the alternative approaches like population bioequivalence and individual bioequivalence assessment approaches arise as different variances like inter/ intra-subject variance and subject-by-formulation variance along with population mean are considered. Objectives: Methoxsalen, in combination with long-wave UVA radiation, is used in the symptomatic management certain psoriasis. The study was aimed to establish the bioequivalence (BE) of a newly developed methoxsalen capsule (MTX test) with that of a reference methoxsalen capsule (MTX reference) using multiple BE methods (i.e., average [ABE], population [PBE], and individual [IBE]) by utilizing a new LC–MS/MS method. Methods: This is an open-label, randomized, balanced, two-treatment, three-period, three-sequence, crossover, single-dose (20 mg, 2 × 10 mg capsules), comparative, oral BE study conducted in 52 healthy, adult males under fasting conditions. Along with various pharmacokinetic (PK) parameters ABE, PBE, and IBE were also determined in the single study. Results: : A non-compartmental model best described the concentration–time data of both MTX test and reference. Both the formulations demonstrated nearly similar values of BE parameters (i.e., AUCo–t, AUC0–∞, Cmax, Tmax, and t1/2). For MTX test, the observed Cmax, AUC0–t, and AUC0–∞ were 125.16±81.53 ng/mL, 313.73±260.86 ng h/mL, and 321.25±271.85 ng h/mL, respectively. For MTX reference, the values were 127.63±71.60 ng/mL, 329.11±252.91 ng h/mL, and 335.48±264.54 ng h/mL, respectively. The bioanalytical method was validated over the concentration range 0.100–100.00ng/mL and the coefficient of determination (r2) was ≥ 0.9991. The sensitivity of the method was 0.100 ng/mL with the accuracy and precision values of 115% and 10.54%, respectively. Conclusion: A single dose of MTX test met the ABE criteria of 80.00% –125.00% for Cmax, AUCo–t, and AUC0–∞, against MTX reference. The study outcome by PBE and IBE approaches proved that MTX Test was bio-inequivalent to MTX reference. Using multiple BE assessment methods in a single BE study is a novel approach and may overcome shortcomings of conventional bioequivalence assessment methods.